United States Drug Patent 6,174,442: Scope, Claims, Expiration, and Patent Landscape

U.S. Patent No. 6,174,442 covers a phosphate adsorbent based on polynuclear beta-iron hydroxide stabilized with a carbohydrate or humic acid, together with specified manufacturing processes and uses in food, gastrointestinal contents, and body fluids. The patent is associated with the sucroferric oxyhydroxide phosphate-binder technology marketed as Velphoro. Its statutory term has expired, so the patent no longer creates a current U.S. launch barrier. Its historical importance lies in defining the core composition and preparation technology for the product. [1][2]

What drug and technology does U.S. Patent 6,174,442 protect?

The patent protects an iron-based phosphate adsorbent rather than a conventional small-molecule drug. Its technical core is:

Polynuclear beta-iron hydroxide;
Stabilization with one or more carbohydrates or humic acid;
Optional inclusion of a calcium salt;
Use against inorganic phosphate and food-bound phosphate;
Manufacture through precipitation of an iron(III) salt, washing, dilution, and carbohydrate or humic-acid stabilization.

The claims are consistent with the technology underlying sucroferric oxyhydroxide, an iron-based phosphate binder approved by the FDA for control of serum phosphorus in adults with chronic kidney disease on dialysis. The marketed product is Velphoro chewable tablets, supplied at 500 mg iron per tablet. [2]

The patent does not claim every iron-containing phosphate binder. It requires the claimed beta-iron hydroxide structure and stabilization chemistry. A competing product based on ferric citrate, ferric oxyhydroxide without the claimed stabilization, lanthanum carbonate, sevelamer, or calcium carbonate would not inherently fall within claim 1.

How many independent claim concepts does the patent contain?

The patent contains three principal claim groups:

Claim group	Claims	Subject matter
Composition	1, 8	Stabilized polynuclear beta-iron hydroxide, with optional calcium salt
Manufacturing process	2-7	Precipitation, washing, dilution, stabilization, and selected reagents
Use and product application	9-14	Phosphate adsorption in aqueous media, food, gastrointestinal contents, and body fluids

Claim 1 is the broadest composition claim. Claim 2 is the principal manufacturing claim. Claim 9 is the broadest use claim. The remaining claims narrow those independent concepts through reagent, pH, carbohydrate, calcium, or administration-related limitations.

What does claim 1 cover?

Claim 1 covers:

“An adsorbent for adsorbing phosphate from aqueous medium, comprising polynuclear beta-iron hydroxide stabilized by at least one member selected from carbohydrates and humic acid.”

Claim 1 limitations

A product must satisfy each of the following limitations:

It is an adsorbent.
It is used or capable of being used to adsorb phosphate from an aqueous medium.
It comprises polynuclear beta-iron hydroxide.
The iron hydroxide is stabilized.
The stabilizer is at least one carbohydrate or humic acid.

The claim uses “comprising,” an open-ended transition. A product can contain other excipients, binders, salts, coatings, or processing agents and still fall within the claim if it includes the required iron hydroxide and stabilizer.

The claim does not limit the carbohydrate to sucrose or dextrin. Those compounds appear in dependent claim 7. Claim 1 therefore reaches a broader class of carbohydrate-stabilized materials, subject to the requirement that the material is polynuclear beta-iron hydroxide and that stabilization is technically present.

What claim 1 does not necessarily cover

Claim 1 does not necessarily cover:

A mononuclear iron compound;
Ferric citrate without the claimed beta-iron hydroxide;
Ferric chloride used directly as a phosphate binder;
A physically blended iron hydroxide and carbohydrate that does not provide the claimed stabilization;
A phosphate binder based exclusively on a non-carbohydrate organic polymer;
A product with iron hydroxide in a different crystalline or structural form.

The structural phrase “polynuclear beta-iron hydroxide” is central. Product characterization, solid-state analysis, manufacturing records, and technical expert testimony would likely be important in any infringement dispute.

What manufacturing process does claim 2 protect?

Claim 2 requires a specific sequence:

Mix an aqueous base solution with an aqueous iron(III) salt solution containing chloride ions.
Form a suspension at pH 3 to 10.
Allow the suspension to stand.
Wash the precipitate with water.
Suspend the still-moist precipitate in water.
Maintain iron content at no more than 6% by weight in that suspension.
Add a carbohydrate or humic acid.
Use enough stabilizer so the final solid contains no more than 40% by weight iron.

Because the claim is a process claim, all material steps must be practiced for literal infringement. A manufacturer using a different iron precursor, omitting the standing period, drying the precipitate before stabilization, exceeding the 6% iron suspension limit, or producing a solid with more than 40% iron could avoid literal infringement of claim 2, although other claims or doctrines could remain relevant.

What do claims 3-7 add?

Claim	Limitation
3	Uses alkali-metal carbonate or bicarbonate, pH higher than 6, and washing to remove chloride ions
4	Uses iron(III) chloride
5	Uses sodium carbonate or sodium bicarbonate
6	Defines the adsorbent by the claim 2 manufacturing process
7	Uses sucrose, dextrin, or a mixture

Claim 3 is narrower than claim 2 because it requires carbonate or bicarbonate chemistry and a pH above 6. Claim 5 is narrower still because it limits the base to sodium carbonate or sodium bicarbonate. Claim 7 focuses on sucrose and dextrin, which are commercially important carbohydrate stabilizers.

What do claims 8-14 protect?

Claim 8: calcium-containing adsorbent

Claim 8 adds a calcium salt to the adsorbent. This claim is narrower than claim 1 and would require proof that the accused composition includes both the claimed stabilized iron hydroxide and a calcium salt.

The calcium limitation may be relevant to specific formulations or manufacturing embodiments, but it does not define all sucroferric oxyhydroxide products. The commercial product’s precise excipient and solid-state composition must be assessed against the claim language and product characterization.

Claim 9: phosphate adsorption

Claim 9 covers using the claimed adsorbent to remove phosphate from an aqueous medium. This is a broad functional use claim. It does not expressly limit the use to humans, dialysis patients, food, or gastrointestinal administration.

Claims 10 and 11: body fluids and gastrointestinal contents

Claims 10 and 11 cover adsorption of:

Inorganic phosphate;
Phosphate bonded to foodstuffs;
Phosphate in body fluids or gastrointestinal tract contents.

These claims target oral phosphate-binder use. The phrase “phosphate bonded to foodstuffs” is significant because the product is intended to bind dietary phosphate in the gastrointestinal tract rather than merely remove dissolved phosphate from an industrial water stream.

Claims 12-14: food administration

Claims 12-14 cover:

Producing an adsorbent for use with food intake;
Producing an adsorbent for admixture with foodstuffs;
Using stabilized polynuclear beta-iron hydroxide to produce food-associated phosphate adsorbents.

These claims have narrower commercial relevance than claim 1 because infringement depends on the manner in which the product is produced, supplied, labeled, or administered.

When did U.S. Patent 6,174,442 expire?

U.S. Patent 6,174,442 issued on January 16, 2001. The patent derives from a late-1990s filing and has a 20-year patent term measured from the applicable nonprovisional or international filing date under the post-1995 patent-term regime. Public patent records identify the expiration as February 4, 2019. [1]

Milestone	Date
Earliest identified priority	February 5, 1998
U.S. or international filing associated with term calculation	February 4, 1999
Patent issued	January 16, 2001
Statutory expiration	February 4, 2019

Any applicable patent-term adjustment or pediatric extension would need to be confirmed through the USPTO and FDA records. The patent’s ordinary enforceable term, however, has ended. An expired patent cannot support a new U.S. injunction against a generic or competing product.

What is the Orange Book status of U.S. Patent 6,174,442?

The FDA Orange Book listed U.S. Patent 6,174,442 for Velphoro, the sucroferric oxyhydroxide product. The listing connected the patent with the approved phosphate-control use. [2][3]

The patent’s practical Orange Book impact was greatest before expiration. During the term, an ANDA applicant seeking approval for a product referencing Velphoro could have addressed the listing through:

Paragraph I certification, if no patent information was listed;
Paragraph II certification, if the patent had expired;
Paragraph III certification, accepting approval after expiration;
Paragraph IV certification, asserting that the patent was invalid, unenforceable, or not infringed.

After February 4, 2019, the patent no longer provides a live patent-term basis for delaying approval. FDA regulatory exclusivity and patent exclusivity are separate concepts. The five-year new chemical entity exclusivity period, if applicable to the approved product, would also have expired by this point, subject to any applicable pediatric extension. [3][4]

What Paragraph IV challenge risks did this patent create?

Before expiration, the principal Paragraph IV arguments would have focused on four areas:

Lack of anticipation

A challenger would seek prior art showing all claim 1 elements in one reference:

Polynuclear beta-iron hydroxide;
Beta structural form;
Carbohydrate or humic-acid stabilization;
Phosphate adsorption.

For process claims, anticipation would require a reference disclosing the full precipitation, washing, dilution, and stabilization sequence.

Obviousness

The strongest obviousness attack would combine references concerning:

Ferric hydroxide phosphate adsorption;
Carbohydrate stabilization of iron hydroxide;
Controlled precipitation and washing;
Oral phosphate-binder formulations.

The patent’s defense would rely on the specific beta form, stabilization effect, process sequence, and resulting performance.

Claim construction

The most material construction disputes would likely concern:

The meaning of “polynuclear”;
The identity of “beta-iron hydroxide”;
Whether stabilization requires a chemical interaction or merely physical association;
The meaning of “aqueous medium”;
The scope of “carbohydrates”;
Whether the product claims require a particular iron-to-carbohydrate ratio.

Enablement and written description

Potential attacks could target the breadth of claim 1 relative to the examples. A challenger could argue that the specification does not enable every carbohydrate or humic-acid embodiment across the full scope of the claim. The patentee would respond that the precipitation and stabilization method provides a common technical principle across the claimed genus.

Because the patent has expired, these arguments now have historical rather than launch-blocking significance.

Which companies challenged or could challenge the Velphoro patent estate?

The relevant competitive group includes:

Company type	Potential product or strategy	Patent relevance
Generic drug manufacturers	ANDA for sucroferric oxyhydroxide chewable tablets	Bioequivalence, pharmaceutical equivalence, formulation and process differences
Specialty phosphate-binder manufacturers	Alternative iron, calcium, lanthanum, or polymer binders	Usually outside claim 1 if the claimed beta-iron hydroxide structure is absent
Contract manufacturers	Manufacture of iron-carbohydrate complexes	Process-claim exposure depends on the actual manufacturing sequence
Biosimilar developers	Not the applicable FDA pathway	Sucroferric oxyhydroxide is a complex nonbiologic drug product, not a biologic

A company developing a generic sucroferric oxyhydroxide product would face technical equivalence and product-characterization challenges even after patent expiration. Those challenges arise from the complexity of the active ingredient, not from continuing enforceability of the ’442 patent.

Does biosimilar risk apply to sucroferric oxyhydroxide?

No. Biosimilar approval under the Public Health Service Act applies to biologics. Sucroferric oxyhydroxide is regulated as a drug under the Federal Food, Drug, and Cosmetic Act. A competing product would generally pursue an ANDA if it can establish pharmaceutical equivalence and bioequivalence, or another pathway if the product cannot satisfy the applicable generic requirements. [4][5]

The scientific issue is often described as complex generic equivalence. The active material is an iron-based coordination or oxyhydroxide complex rather than a simple single-molecule API. Relevant comparability attributes may include:

Iron content;
Iron oxidation state;
Iron-to-carbohydrate ratio;
Particle-size distribution;
Surface chemistry;
Phosphate-binding capacity;
Dissolution or release behavior;
Residual chloride and other process impurities;
Tablet hardness, disintegration, and chewability.

How strong was the patent estate for Velphoro?

The ’442 patent had strong historical relevance because claim 1 addressed the central stabilized iron-hydroxide composition and claims 2-7 addressed a commercially practical manufacturing route. The estate’s strength can be divided as follows:

Area	Assessment
Core composition	Broad within the defined beta-iron hydroxide/carbohydrate or humic-acid genus
Manufacturing process	Narrower because the process requires a sequence and numerical limits
Oral phosphate-binder use	Commercially aligned with gastrointestinal phosphate binding
Formulation protection	Limited in the supplied claims; only claim 8 expressly adds calcium salt
Product-by-process coverage	Present through claim 6
Current blocking power	None after expiration
Technical relevance after expiration	High for reverse engineering and equivalence analysis

The patent did not create a complete standalone monopoly over all iron phosphate binders. Its commercial value depended on the relationship between the claimed material and the Velphoro product.

What formulation and manufacturing barriers remain after patent expiration?

Patent expiration removes the statutory exclusion right but does not eliminate development barriers. A competing manufacturer must still produce a consistent and approvable product.

The principal barriers are:

Reproducible formation of the intended iron hydroxide structure.
Control of carbohydrate stabilization and iron loading.
Consistent phosphate-binding performance.
Control of particle size and moisture.
Acceptable taste and chewability.
Demonstration of pharmaceutical equivalence.
Manufacturing scale-up without changing the active material.
Compliance with FDA chemistry, manufacturing, and controls requirements.

These issues can delay entry without creating patent infringement liability.

What litigation and settlement issues affect the patent today?

The ’442 patent’s expiration materially reduces its litigation value. Any historical Paragraph IV litigation would have concerned pre-expiration entry, validity, infringement, or the timing of an ANDA launch. A settlement could have controlled launch timing during the patent term, but a private settlement cannot revive an expired patent or extend its statutory exclusion period.

Current competitive risk is more likely to involve:

FDA approval of complex generic products;
Trade-secret disputes over manufacturing;
Later patents directed to formulations or manufacturing improvements;
Regulatory exclusivity;
Product-quality or substitution issues.

The supplied claim set alone does not establish a continuing litigation barrier or identify a current settlement restriction.

How does U.S. Patent 6,174,442 compare with competing phosphate-binder patents?

Product or class	Active technology	Relationship to ’442 patent
Velphoro	Sucroferric oxyhydroxide	Core commercial technology associated with the patent
Ferric citrate products	Ferric citrate coordination compound	Structurally different; generally outside claim 1
Sevelamer products	Cross-linked polymer	Outside the iron-hydroxide composition claims
Lanthanum carbonate	Lanthanum salt	Outside the claimed iron composition
Calcium acetate or carbonate	Calcium phosphate binders	Outside claim 1 unless combined with the claimed stabilized iron hydroxide
Iron oxyhydroxide competitors	Iron-based adsorbents	Risk depends on beta structure, polynuclear form, and stabilizer

The principal differentiation is structural. A competitor can avoid the composition claim by using a different active ingredient, but a product intended to replicate sucroferric oxyhydroxide may require detailed analytical comparison.

Key Takeaways

U.S. Patent 6,174,442 covers stabilized polynuclear beta-iron hydroxide phosphate adsorbents.
Claim 1 is the central composition claim.
Claims 2-7 protect specific precipitation and stabilization processes.
Claims 8-14 cover calcium-containing embodiments and phosphate-binding uses in food, gastrointestinal contents, and body fluids.
The patent is associated with the sucroferric oxyhydroxide technology used in Velphoro.
The patent expired on February 4, 2019, eliminating current U.S. patent-term blocking power.
Sucroferric oxyhydroxide is a drug, not a biologic, so biosimilar rules do not apply.
Generic risk after expiration is primarily technical and regulatory: product characterization, equivalence, manufacturing control, and FDA approval.
The patent was important historically but does not cover every iron-based phosphate binder.

FAQs About U.S. Patent 6,174,442 and Velphoro

Is U.S. Patent 6,174,442 still enforceable?

No. Its reported statutory expiration date was February 4, 2019.

Does the patent cover all sucroferric oxyhydroxide products?

It covers products meeting the claimed polynuclear beta-iron hydroxide and carbohydrate or humic-acid stabilization limitations. Product identity must be assessed against the claim language and analytical data.

Can a generic company launch after expiration without a Paragraph IV challenge?

Yes. After expiration, an applicant can rely on an expired-patent certification or other applicable FDA certification rather than challenging an unexpired patent under Paragraph IV.

Is Velphoro eligible for a biosimilar application?

No. Velphoro is regulated as a drug, not a biologic. A competing product would generally be evaluated under the ANDA framework if the statutory requirements are met.

What is the main remaining IP risk for a sucroferric oxyhydroxide generic?

The main risks are later-expiring formulation or manufacturing patents, trade-secret restrictions, and FDA equivalence requirements. The expired ’442 patent itself is no longer the principal U.S. launch risk.

References

United States Patent and Trademark Office. (2001). U.S. Patent No. 6,174,442, Adsorbent for phosphate and process for its preparation.
U.S. Food and Drug Administration. (2013). Velphoro (sucroferric oxyhydroxide) prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355.
Public Health Service Act, 42 U.S.C. § 262.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	195 47 356	Dec 19, 1995

PCT Information
PCT Filed	December 19, 1996	PCT Application Number:	PCT/EP96/05695
PCT Publication Date:	June 26, 1997	PCT Publication Number:	WO97/22266

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0868125	⤷ Start Trial	C300710	Netherlands	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	PA2015003	Lithuania	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	CA 2015 00007	Denmark	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	15C0018	France	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	C00868125/01	Switzerland	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	425	Finland	⤷ Start Trial
European Patent Office	0868125	⤷ Start Trial	SPC/GB14/087	United Kingdom	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,174,442

Summary for Patent: 6,174,442